Centrifugal casting apparatus



Aug. 7, 1945. G. T. PFLEGER 2,381,515

I CENTRIFUGAL CASTING APPARATUS Filed May 11, 1942 4 Sheets-Sheet l 98 INVENTOR Gearge 7, Pf/per ATTORNEY G. T. PFLEGER CENTRIFUGAL CASTING-APPARATUS Aug. 7, 1945.

Filed May 11, 1942 4 Sheets-Sheet 2 l N V ENTOR eore G l/ifleger ATT o R N EY Aug. 7, 1945. G. T. PFLEGER- CENTRIFUGAL CASTING APPARATUS Filed May 11, 1942' llZ 4 Sheets-Sheet 3 N v E N 'r o R 620/96 7 PI /agar ATTORNEY Aug. 7, 1945.- e. T. PFLEGER CENTRIFUGAL CASTING APPARATUS Filed May 11, 1942 4 Sheets-Sheet 4 INVENTOR (kw/9e 7 A ATTORNEY Patented Aug. 7, I945 UNITED STATES PATENT OFFICE 3.381.616 CEN'IRIFUGQL CASTING APPARATUS George '1'. Pfleger, Los Angeles, Calif., assignor to U. 8. Electrical Motors, Inc., Los Angeles, Calif.', a corporation'of California Application May 11, 1942, Serial No. 442,470

19 Claims.

This invention relates to centrifugal castings and more particularly to the casting of an electrically conducting metal into a squirrel cage-for induction motor rotors.

The rotor of an induction motor is formed of a stack of laminations, defining a magnetic core, and a squirrel-cage mounted thereon. The squirrel cage comprises conductors located in slots formed in the laminations, andend'rlngs that complete the electric circuit through the conductor bars. The squirrel cage conductors (bars as difficulties has been suggested, but there are inherent disadvantages to this process when the melting point of the metal ls-r"elatively high.

It is one of the objects of this invention to make it possible to employ centrifugal casting methods for metals having a higher-melting point. than aluminum, for example copper or its alloys.

In providing for centrifugally casting copper or a copper alloy, especially for casting squirrel cages in rotors, the rotor core is mounted in a mold structure and in such manner that the entire mold structure is rotated about the axis of the rotor. It is another object of this invention to provide a simple and easily manipulable mold structure of this character.

It is still another object of this invention to make it possible to control the rate of rotation of the mold, and in such manner that the molten metal may be first distributed adjacent the spaces to be filled, before rapid rotation (with its attendant centrifugal effect) occurs. In this way, a uniform casting, free of blow holes or other defects, can be readily obtained.

It is of considerable importance in connection with casting metals having melting points higher than that of aluminum, to ensure against sudden or rapid chilling ofthe metal. Any such sudden chilling maynot only be q ite harmful to the quality of the casting, but. it may also cause the 7 metal partially at least to congeal before it has filled all-of the" mold spaces. It is accordingly sible retard the cooling of the molten metal.

It is accordingly another object. of this invention to provide means for retarding the transmission of heat from the molten metal, and especially by the use of sand for forming at least part of the mold structure; as well as by preheating at least some of the parts that are to be in heat transfer relation to the cast metal.

' It is another object of this invention to support and reinforce the sand part of the mold so that it will not be disintegrated during the process of centrifugal casting. v

In connection with the castingof squirrel cage rotors, the casting is accomplished in conjunction with a stack of laminations. It is this stack which may be preheated, so as not to produce any sudden chilling of the cast metal. It is obvious,

however, that the motor shaft should not be included with the laminations, since otherwise the shaft would be subjected to a temperature that may necessitate further corrective machining or other treatment after the casting is finished. In lieu of the shaft, an axially extending arbor is provided, which holds the laminations together.

After metal is poured into the mold, the centrifugal action tends to throw the metal radially outwardly, and away from the axis. However, it is advantageous, even when the amount of metal used is measured to comply with the amount needed, to provide some excess; and if no precautions be taken, this excess maybe deposited immediately over the arbor. Under such circumstances, the deposited excess metal would be dimcult. to remove. It is another object of this invention to makeit possible very easily to remove such excess metal, and especially by the provision of a removable cap placed over the end of the arbor. This cap is preferably formed with guiding surfaces to facilitate the uniform distribution of metal in a radial direction into the mold spaces.

It is still another object or this invention to ensure that during the process of casting, the rotor core laminations are compressed tightly to prevent ingress of molten metal between the laminations. I

In many instances it is required to cast fan blades on the end rings of the squirrel cages.

JIhese blades are thin and consequently present a another-object of this"inv'ention to make it poscasting problem, since great care must be taken that the molten metal while forming the blade does not congeal too rapidly. This problem is solved by the aid of this invention by utilizing a sand mold so arranged that it'forms a substantiallycontlnuous layer of heat insulation around the laminations.

.It is still another object of this invention to make it possible readily to assemble the mold parts to form the complete mold. and especially in such manner that a source of rotary motion may be quickly and easily coupled to the mold. This may I specification. These forms will now be described 15 in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limitin sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings: l Figurel is a longitudinal sectional view of one form of apparatus incorporating the invention;

Figs. 2 and 3 are enlarged sectional views taken along correspondingly numbered planes of Fig. 1; Fig. 4 is an exploded pictorial view of the arbor and associated parts to maintain a stack oi rotor laminations in place' during the casting of the squirrel cage therein;

Fig. 5 is a pictorial view of a reinforcement utilized in connection with the sand liners for the mold structure; Fig. 6 is a pictorial view of a stack ofrotor laminations after the casting operation is completed;

Fig. 7 is a view similar to Fig. 1 of a modified 35 form of the invention; I

Fig. 8 is a diagrammatic side elevation of the apparatus shown in Fig. l, with mechanism for supporting and rotating the mold structure; and

excessive cooling. Such sudden or excessive cooling would render the metal not sufliciently fluent during casting, and would also produce highly undesirable irregularities in the cast metal.

The stack 2 of laminations is placed within a mold which cooperates with the stack to provide the mold spaces for the flow of metal to form the integral squirrel cage structure.

In the form of the invention illustrated in Figs. 1, 2 and 3, the stack of laminationsl (Figs. 1 and 2) is shown with its axis in substantially vertical position. The slots 3 of the laminations (Fig. 2)-

- are shown as communicating with the recesses Ill; the squirrel cage conductors arecast so as to fill the recesses III as well as the slots 2.

The stack 2 as illustrated most clearly in Fig. 1 is accommodated so as to be coaxial with an upper mold section II and a lower mold section l2. These mold sections. of shell form, are made from metal and are arranged to be separated by relative axial movement.

The lower portion of the section II is provided with an integral narrow band or flange i3. Into this band or flange telescopes a corresponding upper portion H or the lower section l2.

Means are provided to restrain the two sections II and I! from relative angular movement. For this purpose a key I5 (Fig. 2) is provided on the inner side of the flange l2 and is arranged to be accommodated in a corresponding slot cut in the ring or band ll. In this way the upper and lower sections H and I2 are kept in relative angular alinement to ensure that the mold spaces in the upper and lower sections will be maintained in correct relative positions.

. The mold sections are arranged to be rotated about the axis llof the stack 2. The manner in which this rotation is effected will be described hereinafter.

Fig. 9 is a diagrammatic sectional view taken i0 Metal is arranged to be supplied to the interior along plane 9-! of Fig. 8. I v

The centrifugal casting apparatus is arranged in the present instance to castafsquirrel cage in a magnetic rotor member i. The rotor, as shown most clearly in Fig. 6, includes a series of laminatherecesses near the periphery of the stack 2. In

this instance these recesses are shown as having slots 2 opening in the periphery of the stack. Furthermore, for the purpose of obtaining certain characteristics for the induction motor, the recesses and slots 2 are shown in this instance as of. 5

' as may be provided by the interior surface of skew formation. The conductors in the recesses are joined at each end of the stack 2 to the conductor end rings 4 and I, cast integrally with the bars or conductors. In the'present instances. se-

ries of fan-blades I and I are also cast integrally so The conductors in the recesses of the laminacs tlons 2, the end rings 4 and I. the fan blades Ii. and fl and the pins! and l are integrallyijcast by the aid of the apparatus herein to be descr bed.

The metal utilized for the casting may be of a high melting point such as copper or a copper alloy.

Such copper alloys have a much higher melting point, for example, than aluminum, which can'be cast quite readily. The higher melting point metals and alloys, however. present a more vexing 'of the mold sections H and I2 through the upwardly extending projection l1 formed integrally with the upper section II. This projection is hollow, forming a passageway I. that extends downwardly toward the top of the stack 2.

When molten metal is permitted to flow into the recesses II and slots 2 for forming the bars of the squirrel cage, it is necessary that the flow of the metal radially outwardly beyond the slots should be prevented. This radial flow would occur under the influence of centrifugal force due to the rotation of the mold structure. Accordingly it is necessary to provide a mold surface adjacent the external periphery of the stack 2.

A metal mold surface for this purpose, such the sections H and i2, might chill the metal too rapidly and might cause it therefore to congeal and thereby prevent the metal from flowing into all of the spaces provided by the mold.

In order to ensure that the high melting point apparatus in a well understood way, and are quite self-supporting by appropriate admixture of the sand with adhesive material. The sand liner ll problem, since it is essential to prevent sudden or 15' is provided with a skirt portion 2| that substanand 4). This arbor as is provided with a tially entirely lines the inside of the section II. This skirt portion 2| is in the form of an outer annular flange. Its inner surface closely encompasses the outer periphery of the laminations 2. The corresponding skirt portion 22 of the sand liner 20 similarly lines the inner surface of lower section I2 and also closely encircles the outer periphery of the stack 2. Thus these skirt portions 2| and 22 cooperate to define an outer ring of poor' heat conducting material around the stack 2.

Each of the sand liners l9 and 20 is also provided with an inner flange or band 23-, 24. The end surfaces of these flanges 23 and 24 contact with the ends of the stack 2. The recesses ll] of the stack 2 open into the space between the inner and outer flanges of the liners l9 and 20. Thus between the flanges 2| and 23 the annular space 25 forms the mold for one of the end rings 4; and similarly the annular space 26 inthe lower sand liner 20 forms the mold for the other end ring 5. Communicating with the spaces 25 and 25 are narrow spaces or slots 21 formed in the main body of the sand liners l9 and 20. These slots 21, as shown most clearly in Fig. 3, form the mold spaces for the fan blades 6 or I of Fig. 6. Intermediate these spaces 21 there may be the round recesses'28 defining mold spaces for the pins 8 and 9.

Ingress of molten metal into the mold spaces just defined and into the recess IU of the lamiround head 39 engaging the top end of the stack 2. At its lower end the arbor 38 is provided with a threaded extension 40. Over this threaded extension is placed a collar 4|-and the entire assembly is held in tightened condition by a nut 42.

In order to protect the top of the arbor 38 from being overlaid with cast metal in the process of casting, a protector cap 43 (Figs. 1 and 4) is placed over the head 39. This cap 43 is not fastened to the structure but is simply laid into place as illustrated in Fig. 1. Its outer edge is accommodated in an appropriate recess formed in the lower portion of the inner flange 23. After tion of which is concave, forming a central apex.

nations is provided by several gates 29 (three in this instance) that are formed in the bottom of the inner flange 23, l

The recesses ID of course form a passageway for the molten'metal from the mold space 25 into the mold space 26; but in order to ensure that the flow of metal will occur rapidly into the lower mold space, additional gates are provided between these mold'spaces. gates 30, 3| and 32 (Figs. 1, 2 and 3) are illustrated in the lower mold liner 20. These are in the form of radial slots formed in the inner periphery of the outer flange 22. They coincide in position with similar gates such as 33 formed in the outer flange 2| of the sand liner |9. Accordingly when metal flows through the gates 29, the molten metal is urged by centrifugal force radially outwardly and then into the supplemental gates 30, 3|, etc., to flow downwardly into the lower mold spaces. The metal that fills the gates Three suchthe casting operation is completed, the upper surface of cap 43 may be covered with the cast metal; however, the cap can be simply removed with its overlying solidified layer of metal, and the arbor 38 can be readily removed without difliculty from the stack 2.

The upper surface of the cap 43 is purposely formed as a surface of revolution, a radial sec- In this way as the molten metal drops. on to the upper surface of cap 43, the molten metal is guided gradually by the upper surface to change its direction-to a radial one. This eliminates too sudden a, change in the direction of travel of the molten metal. Not only is a smoother flow for the metal provided, but there is little danger of splashing or the like.

While the arbor 38, tightened as by the aid of the nut 42, may keep the stack 2 of the laminations in tightened condition adjacent the axial aperture 35, the outer edges of the stack may yet have a slight spread. Means are provided to exert a pressure adjacent the outer edges to close any material gaps between the laminations.

. For this purpose pressure is exertedfrom the 30, 3|, etc., is later removed by appropriate machining operations.

The inner flange 24 of the lower sand liner 2|) forms a complete closure for the bottom mold spaces, thereby preventing outward flow of the metal through a hollow lower extension 34 formed on the lower mold section |2.

upper section toward the lower section l2 through the sand liners Hand 23.

' Assuming for this purpose that the lower section i2 is so supported by the aid of the lower extension 34 as to resist rigidly any downward thrust, the upper section U in a manner to be hereinafter described, is resiliently urged down-.-

wardly. It is to. be noted in connection with Fig. 1 that the contiguous end surfaces of the sections H and I2 are slightly separated to permit this compression force to act upon the stack.

Also the contiguous end faces of the outer flanges 2| and 22 are shown as spaced very slightly apart. In this way a pressure exerted upon the upper end of the section it is transmitted through the In order to ensure that no molten metal will now between the laminations comprising the stack 2, means are provided for keeping the stack 2 in compressed condition during the casting op-' eration. For this purpose not only is there an axial fastening means such as an arbor structure illustrated in .Fig. 4, but provisions are also made to exerta compressive force adjacent the edges of the stack 2. There will firstbe described the arbor arrangement which is accommodated in the axial opening 35 of the stack 2.

Each of the, laminations comprising the stack 2 is provided with a key hole slot'36 (Fig. 2).

.. These laminations by the aid of the slots 36 are arranged in definite skew form by the aid of a skew key 31 formed in the arbor 38 (Figs. 1, 2

sand liner H! on to the outer edge of the stack 2.

In order to ensure that the sand liners i9 and 23 will be able to withstand this compression force, each of them is provided with a reinforcement. The reinforcement is in the form of an annular ring 44 shown to' best advantage in Fig. 5.

This ring 44 has one edge 45 that coincides substantially exactly with the outer edge of the stack 2. Each of the reinforcing rings 42 is shown as having apertures 46 by the aid of which it is securely anchored in the corresponding sand liner. It may also be provided with the slots 41, K

corresponding in position with the gates 3'0, 3| and 32. The other edge 48 of the reinforcing ring or band 44 extends to the outer end surface of .the corresponding sandliner l9 or 20. In this way the compressive thrust exerted upon the stack 2 is taken directly on the reinforcing ring.

The other edge 45 is asheretofore stated, in contact with the outer edge of the stack 2. In this way the compressive force is communicated thin the outer edge of the stack; I

In order to impart rotation to the mold structure, the lower extension 34 is shown as seated within a rotary clutch member 49. This clutch member has a central tapered aperture into which the tapered extension 34 seats.

The clutch member 49 is mounted for rotation by the aid of a ball bearing structure 59. This ball bearing structure supports the clutch member 49 both radially and axially. The inner race of this structure is mounted on a cylindrical surface 52 formed on the lower portion of the clutch member 49. The upper surface of the race 5| abuts the shoulder 53. It is held against the shoulder 53 bythe aid of the ring 54 fastened to the clutch member 49 and overhanging the race 5|. The outer race 55 is supported within a stationary supporting member 56 (See also Figs. 8 and 9). This member 56 has a circular flange 51 mounted upon the member 56. Within this flange is located the outer race 55. A top ring 58 fastened to theflange 51 maintains the race 55 in position.

The support 56 as shown most clearly in Figs. 8 and 9 is laterally extended to join a base member 59. This base member 59 embraces the vertical rails 68 formed in upright position on a main supporting frame 6|. This main supporting frame 6| is of columnar form, as illustrated most clearly in Fig. 9. It may be provided with a pedestal 62 disposed upon a convenient level surface, such as the-floor.

The clutch member 49 has an outer peripheral ring portion 63 forming a wheel by the aid of which the clutch member 49 may be rotated. In the present instance ,this wheel 63 may be formed with teeth 64 adapted to cooperate with a driving chain 65. This chain is shown in Fig. 9 as being driven by an appropriately constructed wheel 66 mounted on a load driving shaft 51; This load driving 'shaft is shown .as projecting upwardly from a power transmission casing 68, illustrated in diagrammatic fashion. By appropriate manipulation of the control elements, the speed of the load driving shaft 61 may be varied within relatively wide limits for purposes to be hereinafter described.

The upper hollow extension ll of the mold structure is supported for rotation in a manner similar to that described in connection with the lower extension 34. Thus the outer tapered surface of the extension I! is accommodated within ported and contacted by the clutch ring 69, and may optionally be moved upwardly so as to permit assembly of the mold elements preparatory to casting. When ring is brought downwardly to the proper operative position', the ring 15 may be locked against further movement.

For this purpose the ring 15 may be joined to an integral supporting member 88 similar to supporting member 56 (Figs. 8 and 9). This supporting member-88 in turn is shown as joined to a slide or carriage 8| operating upon the vertical rails 68. These vertical rails 68 thus guide the support 8| in a vertical direction. A clamp screw 82 may be provided formaintaining the support 80 at any height. When loosened however it is possible by the aid of the hand wheel 83, the train of gearing 84 and rack 85 to move a correspondingly tapered bore of a rotary ring pose the outer race 14 is shown as 'slidably mounted in a stationary ring 15. A lower ring 16 is attached to the lower edge of the stationary ring 15. The upper surface of the ring 16 provides a limit to the downward movement of the race 14 in the ring 15.

A number of stiff compression springs 1'! are disposed in appropriate recesses 18 in the ring 15. These springs act downwardly and against a follower ring I9 disposed on top of the slidable outer race 14. a

This ring 69 is supported by a radial and l the carriage or slide 8| in a vertical direction. For this purpose the hand wheel 83 and the train of gearing 84 are supported by the aid of the extension 86 Joined to the slide 8|. The rack 85 is supported on the back of the rails 68.

If desired, a counterweight 81 may be provided for the carriage-8| and its associated-part. This counterweight 81 is shown as connected by a flexible element such as a cable 88 to the eye 89 fastened tothe top of the carriage or slide 8|. 'The flexible cable idler rollers 98.

It may sometimes be advisable to conduct the casting operation in the presence of an inert gas. For this purpose a sheet metal housing or cover member 9| (Figs. 1, 8 and 9) may be provided. This cover member may have a hinged door 92 to gain access to the mold. The cover member 9| may be appropriately supported uponthe supporting standard 56 and may be further provided with apertures such as 93 (Fig. 1) for the pas sage of the reaches of the flexible chain 65.

A supply of the inert gas may be provided through a connection 94 shown at the bottom of Fig. 1, which leads into the tubular extension 95. This tubular extension 95 is fastened to the base or support 56. Inert gas passing through the connection 94 can pass upwardly through the hollow extension 34 and in and around the mold structure, into the casing 9|. Since no attempt is made to make the housing or casing air tight, the inert gas simply flows outwardly of the housing 9|.

In order to facilitate the pouring of the molten metal, a funnel member 96 is provided at the top of the mold structure. This funnel member is shown as fastened to a flat plate 91 fastened to the ring 15. The lower end of the funnel'mem- 88 may pass over several ber may project slightly into the passageway I8 sembled in the clutch ring 49.

The ring 15 is vertically movable so that the tapered extension l1 may be appropriately supdenly chilY the molten metal.

formed in the extension IT.

The use of the mold may now be explained. With the housing 9| open, a lower mold section l2 with its associated sand liner 28 may be as- An assembled stack 2 with its arbor 38 is preheated in a furnace to a red heat, in order that it will not sud- After it is preheated in this manner, the assembled stack 2 with thearbor 38 may be placed in position on top of the inner flange 24 and within the outer flange 22. The loose cap 43 may then be placed over the arbor 38. Then the upper section II with its associated sand liner l9 may be moved axially to the position illustrated in Fig. 1, the key l5 engaging the corresponding slot in the lower section II. Inthis way it is assured that the gate passages 38, 33, etc., will be in alinement.

. tation may begin at 300 R.

ting ready removal It has been stressed hereinbefore'that the stack of laminations 2' must be preheated to a red heat in order to maintain the molten metal against While these operations have taken place, the slide or carriage BI is in its upper position. When the upper mold section I I is assembled, the hand wheel 83 is operated to bring the ring 59 into clutching engagement with the extension I1. The slide is then clamped against further vertical movement by the aid of the clamp screw 82. The springs 11 operate to provide a resilient force constantly urging the two sections II and [2 toward each other, and to maintain the outer edges of the stack 2 in compressed position.

The door 92 is then closed. The motor drive is now started, imparting relatively slow rotation to the mold structure. With a rotor structure of six or eight inches in diameter, the rate of ro- P. M. While rotating at this slow rate, a measured quantity of the molten copper or copper alloy is poured from a ladle into the funnel 96. after all of the measured quantity of metal has been poured and sufilcient time elapsed for the metal to reach the lower portions of the mold, the rate of rotation is increased to about 800 R. P. M. The period of slow rotation thus occurs substantially to the time when the pouring is completed. The slow rotation ensures that the metal being poured is properly distributed through the gates and mold spaces. During the pouring process, the concavely curved upper surface of cap 43 guides the molten metal smoothly and gradually toward the gates 29, 30,

etc.

The higher rate of rotation of about 800 R. P. M. produces the desired centrifugal force to ensure that even the narrow fan blades 6 and 1 and the small circular projections and 9 are completely cast, and the molten metal completely till the mold spaces for these elements.

The high rate of rotation is continued for about fifteen seconds. The sand liners, in conjunction with the preheating of the stack 2 to a red heat, ensures that the molten metal will not be chilled too rapidly.

If sufficient care is taken in measuring the required amount of molten metal that is deposited through the funnel 96, very little excess metal need be removed from the east product. A thin tubular riser may be formed within the passageway I8; but this may be readily machined off.

When the casting is cooled sufiiciently, the slide or carriage III is moved upwardly and the door 92 is opened. If the mold structure does not readily separate from the clutch ring 49, a slight blow upon the bar 98- (Figs. 1 and 8) upwardly may bring the head 90 against the lower end of the extension 34 to force this extension 34 upwardly. Then upper section II may be removed.

The bar 98 is maintained in its inactive position by aid of its head 09, guided by a wall I00 disposed within the extension 95. This wall I00 is provided with a series of apertures IOI to permit the ingress of inert gas to the housing 9|.

After section II is removed, the rotor stack 2 may be taken out or the lower section I2. The

*cap 43 can bereadily removed without difllculty,

39 of the arbor 38 and permitof the arbor 38 from the stack.

e osing the head rapid congealing. It is possible to provide the preheating of the stack in other ways. For example, in the f rm of the invention illustrated in Fig. 'l, the stack I02 is shown as heated by inductionby the aid of an induction coil I03 shown diagrammatically as disposed around the mold structure. The induction heating may occur prior to the pouring of the metal, as heretofore described.

The upper and lower mold sections I04 and I05 in this instance are shown as accommodating sand mold portions I06 and I0I that do not form a complete lining for the interior surfaces of the sections I04 and I05. Instead, the outer periphcry of the stack I02 is closely spaced with the inner surfaces of these sections I04 and I05.

Pressure upon the outer edge of the stack I02 is accomplished by the shoulders I00 formed along the inner edges of the sections I04 and I05. Furthermore, these sections are radially split as for example into three segments for facilitating their assembly with the sand molds I00 and I01,

.Thus these sand molds I06 and I0! are shown as disposed between the shoulders I09 and the ends of the sections I04, I05. Accordingly in order to assemble the sand molds I06, I01 in place, the three segments of each section I04 and I05 are placed one at a time in proper relationship with the sand molds.

In this instance the arbor H0 for the stack I02 is shown as formed integrall with a head I I I having for the metal poured through the hollow extension I I2.

Provisions for resiliently urging the section I00 downwardly against the stack I02, and for rotation of the mold structure may be the same as shown in Fig. 1.

Since metal parts are in juxtaposition with the outer periphery of stack I02, as represented by the annular portions of sections I04 and I05, these metal portions may produce an undesirable chilling effect, Accordingly it-is desirable to preheat these mold sections before the metal is cast. In the present instance this may be accomplished by the aid of the induction coil l03 since this induction coil I03 may serve to induce current both in the metal sections I04 and I05 as well as in the stack I02. The resistivity of the material forming the sections I04 and I05 may be. definitely chosen to produce the desired heating effect. For example, this resistivity may be quite high in Stainless steel is a suitable material for this purpose. Since the inner flanges II3 of the sand molds I06 and I01 are not in direct contact with the ends of the laminations, the centrifugal force is depended upon to ensure that the metal will not flowoutwardly over the edges of these flanges IIB. In other respects the process of casting is the same asthat described in connection with Fig. 1.

What is claimed is:

1. In -a rotary mold for centrifugal'casting, separable mold sections, one of said sections defining a tapered clutching surface, a cooperating rotary clutching member for engaging said surface, and means for relatively axially moving the clutching member into and out of cooperating relation with said surface.

2. In a rotary mold for centrifugal casting, separable mold-sections, said mold sections defining a hollow externally tapered extension, coaxial with the axis of rotation, clutching means cooperating with said extension, and'means facilitating thepouring of molten metal into said extension. h

3. In a rotary mold for centrifugal casting,

means forming tapered coaxial extensions for the an appropriate guiding concave surface an end ring, and means mold, a driving clutching member cooperating with one of the extensions, a rotatable member cooperating with the other extension, and means for adjusting the relative positions of said mem bers in a direction corresponding to the direction of the axis of rotation of the mold.

4. In a rotary mold for centrifugal casting, means forming tapered coaxial extensions for the mold, a driving clutching member cooperating with one of the extensions, a rotatable member cooperating with the other extension, and means for adjusting the relative positions of said members in a direction corresponding to the direction of the axis of rotation of the mold, one of said extensions being hollow for the reception of molten metal. a I 5. In a rotary mold for centrifugal casting, a pair of rotary members adapted to cooperate with opposite ends of the mold for driving and supporting said mold, a bearing .structure provided 'for one of said members, an axially adjustable support for said bearing structure, and resilient means carried by the support for urging said member toward cooperative position with respect to the mold end.

6. A rotary mold structure having opposite tapered ends, a pair of rotary members cooperatingv with said ends for driving and supporting said mold, an axially adjustable support for'one of said members, and resilient means carried by the support for urging said member toward cooperative position with respect to the corresponding tapered end.

7, In combination, a sectional mold structure forming a hollow enclosure, means for supporting, within said structure, an assembled stack of rotor laminations and disposed about an axis,the mold spaces being thus partly defined by said stack, the separation of the sections of said mold occurring by relative movement of the sections in an axial direction, a sand liner for each of the mold sections, each of said liners including an annular reinforcing band, means for transmitting a resilient force through one of the sections and the reinforcing band associated with the liner for said section, for exerting a pressure on said stack, and means for rotating said structure about said axis.

8. In combination, a sectional mold structure forming a hollow enclosure, means for supporting, within said structure, an assembled stack of rotor laminations and disposed about an axis, the mold spaces being thus partly defined by said stack, the separation of the sections of said mold occurring by relative movement of the sections in an axial direction, a sand liner for each of the mold sections, said liner having a pair of radially spaced flanges, the 'outer flange forming the lining proper, and the inner flange cooperating with the end of the stack to define a mold space for for rotating said structure about said axis. 1

9. In combination, a sectional mold structure forming a hollow enclosure, means for supporting, within said structure, an assembled stack of rotor laminations and disposed about an axis, the mold spaces being thus partly defined by said stack, the sections of said mold occurring-by relative movement of the sections in an axial direction, a sand liner for each of the mold sections, said liner having a pair of radially spaced flanges, the outer flange forming the lining proper, and the inner flange cooperating with the end of the stack to define a mold space for an end ring, there being recesses in the liner extending outtend from the top wardly of the end ring spaces, for forming fan blades on said rings, and means for rotating said structure about said axis.

10. In combination, a sectional mold structure forming a hollow enclosure, means for supporting, within said structure, an assembled stack of rotor laminations and disposed about an axis, the mold spaces being thus partly defined by said stack, at least one of said sections having a hollow projection through which molten metal may be supplied to the mold spacer, and means 00- operating with said hollow projection for rotating said structure about said axis.

11. In a rotary mold for centrifugal casting, a pair of metal sections. defining a hollow space, means cooperating with the sections for rotating the mold, and a sectional sand liner for the mold sections, said liner completely encircling said stack, and having inwardly directed portions cooperating with the stack to define mold spaces for end rings.

12. In a rotary mold for centrifugal casting, a pair of metal sections, defining a hollow space, means cooperating with the sections for rotating the mold, a sectional sand liner for the mold sections, and adapted to cooperate with a stack of rotor laminations to define the mold spaces, said stack having a substantially vertical axis about'which the mold is rotated, means forming a passageway from the top of the stack for the metal to be cast and a cap disposed over the central portion of the top of the stack, said upper sand liner having a number of gates for the entry of the metal from above the cap and radially outwardly and downwardly into the lower liner.

13. In a rotary mold for centrifugal casting, a pair of metal sections, defining a hollow space;

means cooperating with the sections for rotating the mold, a sectional sand liner for the mold sections, and adapted to cooperate with a stack of rotor laminations to define the mold spaces, said stack having a substantially vertical axis about which the mold is rotated, means forming a passageway from the top of the stack for the metal to be castand a cap disposed over the central portion of the top of the stack, said upper sand liner having a number of gates for the entry of the metal from above the cap and radially outwardly and downwardly into the lower liner, said cap having an upper guiding surface for gradually changing the direction of the flow of metal from vertical to radial.

14. In a rotary mold for centrifugal casting, a pair of metal sections, defining a hollow space, means cooperating with the sections for rotating the mold, and a sectional sand liner for the mold sections, and adapted to cooperate with a stack of rotor laminations to define the mold spaces, the rotation being about a substantially vertical axis, and the lower portion of the sand liner forming a. closed bottom preventing flow oi! metal downwardly.

15. In a rotary mold for centrifugal casting, a

pair of metal sections, defining a hollow space,

.ends of the stack for end rings, and having an inner periphery encircling the outer periphery oi the stack, except for one or more gates that exto the bottom 01' the stack and defining a flow space for the metal exterior of the stack, said inner periphery otherwise confining the flow of metal into the mold spaces for the end rings and into the spaces for the squirrel cage bars.

16. In centrifugal casting apparatus, an uppe section, a lower section, said sections defining a mold space and adapted to be rotated on a substantially vertical axis, said sections being separable by relative movement in an axial direction, said space being adapted to cooperate with a stack of laminations, and extensionsprojecting axially from the sections and supporting the sections-for rotation.

17. In a centrifugal casting apparatus, a sectional mold structure having a substantially vertical axis of rotation, and defining a mold space, said structure having apair of sections, trans versely divided, each section being formed of -'a plurality of segments longitudinally arranged with respect to the mold axis, said mold space being adapted tocooperate with a stack of laminations, and said segments having extensions cooperating with each other to define a means for supporting the structure for rotation.

18. In combination, a sectional mold structure forming a hollow enclosure, means for supporting, within said structure, an assembled stack of rotor laminations, the mold spaces being thus partly defined by said stack, said sections being separable by relative movement in a direction axial of the stack, a sand liner for each of said mold sections,

each of said liners including a reinforcement at least partly embedded in the liner, and means for transmitting a compressive force through one of the sections and the associated liner upon said stack.

19. In combination, a sectional mold structure forming a hollow enclosure, means for supporting, within said structure, an assembledstack of rotor laminations, the mold spaces being thus partly defined by said stack, said sections being separable by relative movement in a directional axial of the stack, and a sand liner for each of the mold sections, each of said liners having a pair of radially spaced flanges, the outer flange forming the lining proper, and the inner flange co-operating with the corresponding end of the stack to define a mold space for an end'ring.

GEORGE T. PF'LEGER. 

